Foldable display apparatus and manufacturing method thereof

ABSTRACT

A foldable display apparatus includes: a foldable display panel having a folding portion about which display panel is configured to fold; a lower film on one surface of the display panel having two, spaced bumps disposed adjacent to and at opposite sides of the folding portion; and a sub-layer disposed on the lower film, wherein the folding portion is configured to fold so that the display panel faces exteriorly of the display panel and the sub-layer faces interiorly of the display panel, and wherein a sum of heights of the two bumps is approximately less than or equal to a sum of thicknesses of the two sub-layers at respective sides adjacent to the folding portion.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Division of U.S. patent application Ser. No.16/123,693, filed on Sep. 6, 2018, which claims priority from and thebenefit of Korean Patent Application No. 10-2017-0113955, filed on Sep.6, 2017, each of which is hereby incorporated by reference for allpurposes as if fully set forth herein.

BACKGROUND Field

Exemplary embodiments of the invention relate generally to a foldabledisplay apparatus in which a main body may be folded or unfolded, and,more particularly to an apparatus that facilitates folding with reducedinterference from bumps formed during manufacture, as well as amanufacturing method thereof.

Discussion of the Background

Flat display apparatus such as an organic light-emitting displayapparatus may be flexibly deformed, and thus may be manufactured to havea foldable structure for better portability.

Conventionally, manufacturing such a foldable flat display apparatusincludes a step of removing a protective film on a folding portion todecrease the thickness thereof, to facilitate a folding operation. Inthe removing step, a protruding portion, which is so-called a bump, maybe incidentally formed around a portion where the protective film isremoved. The bump causes interference during folding, which may preventor impede a folding operation.

The above information disclosed in this Background section is only forunderstanding of the background of the inventive concepts, and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Exemplary embodiments provide improved foldable display apparatuses thatfacilitate folding with reduced interference from bumps, andmanufacturing methods thereof.

Additional aspects will be set forth in the detailed description whichfollows, and, in part, will be apparent from the disclosure, or may belearned by practice of the inventive concepts.

According to one or more embodiments of the invention, a method ofmanufacturing a foldable display apparatus may include the steps of:disposing a protective film on one surface of a foldable display panelhaving a folding portion; removing at least a part of the protectivefilm in the folding portion of the foldable display panel; anddecreasing a height of at least one bump protruding from the protectivefilm formed adjacent to the removed part of the protective film.

The step of decreasing a height of at least one bump may includeabrading the at least one bump.

The step of removing at least a part of the protective film may includeheating and melting away the part of the protective film correspondingto the folding portion.

The at least one bump may include two bumps respectively formedsymmetrically at each side of the removed part of the protective film.

The step of decreasing a height of at least one bump may includedecreasing a height of both of the two bumps formed symmetrically atrespective sides of the removed part of the protective film, so that thetwo bumps have substantially the same height.

The bumps at the respective sides may protrude upwardly from a surfaceof the protective film.

The bumps at the respective sides may have no portion that protrudesabove a surface of the protective film.

The two bumps may be formed asymmetrically to have different heights ateach side.

The step of decreasing a height of at least one bump may includeabrading only one of the two bumps.

The step of decreasing a height of at least one bump may include:forming one of the bumps to have a generally concave bump; and formingthe other bump to have a generally convex bump, wherein the convex bumpand the concave bump may have conforming shapes that may be nestedtogether when the foldable display apparatus is a folded state.

The method may further include disposing a sub-layer on the protectivefilm.

The step of decreasing a height of at least one bump may includedecreasing the height of at least one bump such that a sum of heights ofthe two bumps at respective sides of the folded area when folded is lessthan or equal to twice a thickness of the sub-layer.

The sub-layer may include: a heat sink plate disposed on the protectivefilm; and a cushion film disposed on the heat sink plate.

The folding portion may be configured to be folded such that the displaypanel faces outwardly and the protective film faces inwardly.

According to one or more embodiments of the invention, a foldabledisplay apparatus may include: a foldable display panel having a foldingportion about which display panel is configured to fold; a protectivefilm on one surface of the display panel having two, spaced bumpsdisposed adjacent to and at opposite sides of the folding portion; and asub-layer disposed on the protective film, wherein the folding portionis configured to fold so that the display panel faces exteriorly of thedisplay panel and the sub-layer faces interiorly of the display panel,and wherein a sum of heights of the two bumps is approximately less thanor equal to a sum of thicknesses of the two sub-layers at respectivesides adjacent to the folding portion.

The two bumps may have substantially the same height and the height ofeach bump is approximately less than or equal to a thickness of thesub-layer.

The two bumps may have different heights and the height of at least oneof the bumps may be approximately less than a thickness of thesub-layer.

The heights of each of the two bumps may be approximately less than orequal to a thickness of the protective film.

The two bumps may include a concave bump and a convex bump havingconforming shapes configured to be nested together when the foldabledisplay apparatus is in a folded state.

The total height of the concave bump and the convex bump in the nested,folded state may be approximately less than or equal to a sum ofthicknesses of the two sub-layers at respective sides adjacent to thefolding portion.

Additional features of the inventive concepts will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the inventive concepts.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the inventive concepts, and are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments of the inventive concepts, and, together with thedescription, serve to explain principles of the inventive concepts.

FIGS. 1A and 1B are cross-sectional views respectively illustrating anunfolded (or expanded) state and a folded (or compact) state of anembodiment of a foldable display apparatus constructed according to theprinciples of the invention.

FIGS. 2A, 2B, 2C, 2D, and 2E are cross-sectional views sequentiallyillustrating an exemplary manufacturing process of the foldable displayapparatus of FIGS. 1A and 1B, according to the principles of theinvention.

FIGS. 3A, 3B, 3C, and 3D are cross-sectional views sequentiallyillustrating another exemplary manufacturing process of a foldabledisplay apparatus, according to the principles of the invention.

FIGS. 4A, 4B, 4C, and 4D are cross-sectional views sequentiallyillustrating yet another exemplary manufacturing process of a foldabledisplay apparatus.

FIGS. 5A, 5B, 5C, and 5D are cross-sectional views sequentiallyillustrating another exemplary manufacturing process of a foldabledisplay apparatus.

FIG. 6A is a plan view of the display panel illustrated in FIG. 1A.

FIG. 6B is a cross-sectional view illustrating an internal structure ofthe display panel of FIG. 6A.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments or implementations ofimplementations of the invention. As used herein “embodiments” and“implementations” are interchangeable words that are non-limitingexamples of devices or methods employing one or more of the inventiveconcepts disclosed herein. It is apparent, however, that variousexemplary embodiments may be practiced without these specific details orwith one or more equivalent arrangements. In other instances, well-knownstructures and devices are shown in block diagram form in order to avoidunnecessarily obscuring various exemplary embodiments. Further, variousexemplary embodiments may be different, but do not have to be exclusive.For example, specific shapes, configurations, and characteristics of anexemplary embodiment may be used or implemented in another exemplaryembodiment without departing from the inventive concepts.

Unless otherwise specified, the illustrated exemplary embodiments are tobe understood as providing exemplary features of varying detail of someways in which the inventive concepts may be implemented in practice.Therefore, unless otherwise specified, the features, components,modules, layers, films, panels, regions, and/or aspects, etc.(hereinafter individually or collectively referred to as “elements”), ofthe various embodiments may be otherwise combined, separated,interchanged, and/or rearranged without departing from the inventiveconcepts.

The use of cross-hatching and/or shading in the accompanying drawings isgenerally provided to clarify boundaries between adjacent elements. Assuch, neither the presence nor the absence of cross-hatching or shadingconveys or indicates any preference or requirement for particularmaterials, material properties, dimensions, proportions, commonalitiesbetween illustrated elements, and/or any other characteristic,attribute, property, etc., of the elements, unless specified. Further,in the accompanying drawings, the size and relative sizes of elementsmay be exaggerated for clarity and/or descriptive purposes. When anexemplary embodiment may be implemented differently, a specific processorder may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order. Also, like reference numerals denote like elements.

When an element, such as a layer, is referred to as being “on,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, connected to, or coupled to the other element or layer orintervening elements or layers may be present. When, however, an elementor layer is referred to as being “directly on,” “directly connected to,”or “directly coupled to” another element or layer, there are nointervening elements or layers present. To this end, the term“connected” may refer to physical, electrical, and/or fluid connection,with or without intervening elements. Further, the D1-axis, the D2-axis,and the D3-axis are not limited to three axes of a rectangularcoordinate system, such as the x, y, and z-axes, and may be interpretedin a broader sense. For example, the D1-axis, the D2-axis, and theD3-axis may be perpendicular to one another, or may represent differentdirections that are not perpendicular to one another. For the purposesof this disclosure, “at least one of X, Y, and Z” and “at least oneselected from the group consisting of X, Y, and Z” may be construed as Xonly, Y only, Z only, or any combination of two or more of X, Y, and Z,such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although the terms “first,” “second,” etc. may be used herein todescribe various types of elements, these elements should not be limitedby these terms. These terms are used to distinguish one element fromanother element. Thus, a first element discussed below could be termed asecond element without departing from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,”“above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), andthe like, may be used herein for descriptive purposes, and, thereby, todescribe one elements relationship to another element(s) as illustratedin the drawings. Spatially relative terms are intended to encompassdifferent orientations of an apparatus in use, operation, and/ormanufacture in addition to the orientation depicted in the drawings. Forexample, if the apparatus in the drawings is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below.Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90degrees or at other orientations), and, as such, the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof. It is also noted that, as used herein, the terms“substantially,” “about,” and other similar terms, are used as terms ofapproximation and not as terms of degree, and, as such, are utilized toaccount for inherent deviations in measured, calculated, and/or providedvalues that would be recognized by one of ordinary skill in the art.

Various exemplary embodiments are described herein with reference tosectional and/or exploded illustrations that are schematic illustrationsof idealized exemplary embodiments and/or intermediate structures. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should notnecessarily be construed as limited to the particular illustrated shapesof regions, but are to include deviations in shapes that result from,for instance, manufacturing. In this manner, regions illustrated in thedrawings may be schematic in nature and the shapes of these regions maynot reflect actual shapes of regions of a device and, as such, are notnecessarily intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

FIGS. 1A and 1B are cross-sectional views respectively illustrating anunfolded (or expanded) state and a folded (or compact) state of anembodiment of a foldable display apparatus 100 constructed according theprinciples of the invention.

The foldable display apparatus 100 may include a display panel 120 thatis flexible and bendable, a protective film 110 attached on one surfaceof the display panel 120, and a sub-layer 130 including a heat sinkplate 131 and a cushion film 132 provided over the protective film 110.The display panel 120 has a structure including a thin film transistorand a light-emitting device to produce an image, an encapsulation layercovering and protecting the thin film transistor and the light-emittingdevice, etc. stacked on and above a flexible substrate. Since thedisplay panel 120 includes the flexible substrate instead of a hardglass substrate, the display panel 120 may be freely folded and unfoldedwithin a permissible range according to its flexibility. Accordingly, ina compact state, the foldable display apparatus 100 may have improvedportability after being folded as illustrated in FIG. 1B.

The foldable display apparatus 100 may be accommodated in an exteriorcase.

The foldable display apparatus 100 is folded such that the display panel120 is located outside and the protective film 110 and the sub-layer 130are located inside. In other words, a lower surface of the display panel120 of FIG. 1A, which is configured to display an image to be viewed bya user, may be folded to be exposed to the outside in the compact state.

A folding portion A defines a portion where the foldable displayapparatus 100 may be folded and unfolded, and the protective film 110 isremoved in the folding portion A to facilitate a folding operation. Inother words, by removing a portion of the protective film 110corresponding to the folding portion A, the total thickness of thefoldable display apparatus 100 in the folding portion A may be decreasedso that the foldable display apparatus 100 may be smoothly folded andunfolded. Also, the folding portion A avoids becoming a starting pointfor exfoliation of the protective film 110 in response to repeatedfolding and unfolding motions.

Referring to FIG. 2B, a protrusion or a bump 111 may be incidentallyformed in a process of removing the protective film 110 in the foldingportion A. In other words, the protective film 110 in the foldingportion A is removed by contacting a heating element such as a heatblock 200 with the protective film 110 in the expanded position to heatand melt away the protective film 110 in the folding portion A. In thisstate, part of the removed portion of the protective film 110 in thefolding portion A is pushed up at both sides, forming the bump 111protruding upward nearby.

The bump 111 may not cause any problem if the bump 111 does not causeany interference in the folded state as illustrated in FIG. 1B. However,when the protruding height of the bump 111 is greater than the thicknessof the sub-layer 130, the foldable display apparatus 100 may not beproperly folded because the bumps 111 at opposing sides may contact eachother.

To address the above problem, in the exemplary embodiments, asillustrated in FIG. 2C, using a abrader 300, which may be a grinder orother device that removes material from the bump 111 by grinding,eroding or other mechanical type process that reduces the first heighth1 of the bump to a second height h2, which is less than or equal to athickness h3 of the sub-layer 130. According to this exemplaryembodiment, the bump 111 may have reduced interference during foldingand unfolding of the foldable display apparatus 100, and thus thefoldable display apparatus 100 may have an improved and more stablefolding operation.

FIG. 6A is a plan view of the display panel illustrated in FIG. 1A, andFIG. 6B is a cross-sectional view illustrating an internal structure ofthe display panel of FIG. 6A. A detailed manufacturing process of thefoldable display apparatus 100 including the abrading of the bump 111 isdescribed later. Prior to the description of the manufacturing processof the foldable display apparatus 100, an internal structure of thedisplay panel 120 is briefly described below with reference to FIGS. 6Aand 6B.

FIG. 6A schematically illustrates a planar structure of the displaypanel 120, which includes a display area DA displaying an image and anon-display area NDA adjacent to the display area DA. The display areaDA includes a plurality of pixel areas PA, and a pixel emitting a lightis formed in each of the pixel areas PA. An image is formed by thelights emitted from a plurality of pixels provided in the display areaDA.

The non-display area NDA may be arranged to surround the display areaDA, and may include a driving unit such as a scan driving unit and adata driving unit to transmit signals to the pixels provided in thedisplay area DA.

FIG. 6A illustrates a case in which the non-display area NDA surroundsthe display area DA. However, the exemplary embodiments are not limitedthereto. Accordingly, for example, the non-display area NDA may bearranged at only one side of the display area DA to reduce an area ofthe non-display area NDA where an image is not displayed, that is, adead area.

Referring to FIG. 6B, one of the pixel areas PA of the display area DAincludes a thin film transistor 121 and an organic light-emitting device122. First, according to the structure of the thin film transistor 121,a buffer layer 121 a is disposed on a flexible substrate 123 disposed ofa polyimide material, an active layer 121 f is disposed over the bufferlayer 121 a, and the active layer 121 f includes source and drainregions in which N-type or P-type impurities are doped at a highconcentration. The active layer 121 f may be disposed of oxidesemiconductor. For example, the oxide semiconductor may include oxide ofa material selected from Group 12, Group 13, and Group 14 metal elementssuch as Zn, In, Ga, Sn, Cd, Ge, or Hf, and a combination thereof. Forexample, a semiconductor active layer 212 may includeG-I-Z-O[(In₂O₃)a(Ga₂O₃)b(ZnO)c], where “a”, “b”, and “c” are realnumbers respectively satisfying conditions that a≥0, b≥0, and c>0. Agate electrode 121 g is disposed over the active layer 121 f with a gateinsulating film 121 b interposed therebetween. A source electrode 121 hand a drain electrode 121 i are disposed over the gate electrode 121 g.An interlayer insulating film 121 c is disposed between the gateelectrode 121 g, the source electrode 121 h, and the drain electrode 121i. A passivation film 121 d is disposed between the source electrode 121h, the drain electrode 121 i, and an anode electrode 122 a of theorganic light-emitting device 122.

An insulating planarization film 121 e, such as acryl, is disposed overthe anode electrode 122 a. After an opening 122 d is disposed in theinsulating planarization film 121 e, the organic light-emitting device122 is disposed.

The organic light-emitting device 122 emits light of red, green, andblue colors according to the flow of current to display imageinformation. The organic light-emitting device 122 may include the anodeelectrode 122 a connected to the drain electrode 121 i of the thin filmtransistor 121 to receive a positive voltage therefrom, a cathodeelectrode 122 c covering the entire pixel to receive a negative voltage,and an emission layer 122 b disposed between the anode electrode 122 aand the cathode electrode 122 c to emit light.

A hole injection layer (HIL), a hole transport layer (HTL), an electrontransport layer (ETL), an electron injection layer (EIL), etc. may bestacked adjacent to the emission layer 122 b.

For example, the emission layer 122 b may be separately formed for eachpixel so that pixels emitting the light of red, green, and blue colorsconstitute a unit pixel. The emission layer 122 b may be commonly formedacross the entire pixel area regardless of the location of a pixel. Theemission layer 122 b may be formed by vertically stacking or mixinglayers including an emission material emitting the light of, forexample, red, green, and blue colors. Colors of each pixel may becombined to emit light having multiple colors including a white light.Furthermore, a color change layer or a color filter that converts theemitted white light to a specific color may be further provided.

A thin film encapsulation layer including an organic film and aninorganic film alternately stacked may be disposed over the cathodeelectrode 122 c.

According to the exemplary embodiments, the display panel 120, which isflexible and foldable according to folding and unfolding operations, maybe used in the foldable display apparatus 100.

FIGS. 2A, 2B, 2C, 2D, and 2E are cross-sectional views sequentiallyillustrating an exemplary manufacturing process of the foldable displayapparatus of FIGS. 1A and 1B, according to the principles of theinvention.

First, as illustrated in FIG. 2A, the protective film 110 is disposed onone surface of the display panel 120. The protective film 110 may beformed of a polyethylene terephthalate resin (PET) material.

Next, as illustrated in FIG. 2B, the heating element 200 is moved tocontact the protective film 110 in the folding portion A, therebymelting and removing a contacting portion of the protective film 110that contacts the heating element 200. In this state, part of thecontacting portion is pushed aside toward opposing boundaries of thefolding portion A, incidentally forming a protrusion, that is, the bump111.

When the bumps 111 at the opposing sides are left untreated, during afolding operation later, the bumps 111 at the opposing sides may contacteach other, preventing or impeding the folding operation, and thus thefoldable display apparatus 100 may not be properly, completely, and/oreasily folded. Accordingly, as illustrated in FIG. 2C, the bumps 111 atthe opposing sides are abraded using the abrader 300, thereby decreasingthe height of the bumps 111. In other words, the bump 111 having a firstheight h1 is reduced to a second height h2, which is less than the firstheight h1. The second height h2 of the bumps 111 after abrading is lessthan or equal to a thickness h3 of the sub-layer 130 that issubsequently stacked on the protective film 110, as illustrated in FIG.2D.

Referring to FIG. 2E, an upper surface of the bump 111 is abraded to beflat so that the height of the bump 111 is decreased to the secondheight h2, which is less than or equal to the thickness h3 of thesub-layer 130. Accordingly, no obstacle to folding is formed in thespace or interval between the sub-layers 130 facing each other from thebumps 111 that interferes with the opposing sides contacting each otherduring the folding of the foldable display apparatus 100. Thus, when thesub-layers 130 at the both sides of the folding portion A contact eachother, a improved and/or stable folded state may be maintained.

According to the exemplary embodiments, the bump 111 formed by removingthe protective film 110 may be abraded to remove or reduce the bump fromimpeding folding the foldable display apparatus 100, and the foldingoperation of the foldable display apparatus 100 may be improved and/orstabilized, and thus improving the quality and reliability of thefoldable display apparatus.

According to the exemplary embodiment illustrated in FIGS. 2A, 2B, 2C,2D, and 2E, the bumps 111 at both sides of the folding portion A areabraded to have substantially the same second height h2 whilemaintaining a protruding shape. However, the exemplary embodiments arenot limited thereto.

FIGS. 3A, 3B, 3C, and 3D are cross-sectional views sequentiallyillustrating another exemplary manufacturing process of a foldabledisplay apparatus, according to the principles of the invention, inwhich only one of the bumps 111 is abraded.

As illustrated in FIG. 3A, the manufacturing process of a foldabledisplay apparatus according to the exemplary embodiment is substantiallythe same as that of the exemplary embodiment illustrated in FIGS. 2A and2B until the steps of attaching the protective film 110 on the displaypanel 120 and removing the folding portion A.

In this embodiment, however, not all of the bumps 111 at both sides ofthe folding portion A that are incidentally formed are abraded, but onlythe bump 111 at one side is abraded using the abrader 300 to have thesecond height h2, as illustrated in FIG. 3B. Next, as illustrated inFIG. 3C, the sub-layer 130 is stacked. Referring to FIG. 3D, even thoughthe height of only one side is decreased, the formation of an obstaclein the space or interval between the folded sub-layers 130 that impedesor prevents proper folding of the foldable display apparatus 100 isavoided. Accordingly, the sum of the first height and the second heighth1+h2 of the bumps 111 at both sides in the folded position is less thanor equal to twice the thickness h3 of the sub-layer 130.

FIGS. 4A, 4B, 4C, and 4D are cross-sectional views sequentiallyillustrating yet another exemplary manufacturing process of a foldabledisplay apparatus.

As illustrated in FIG. 4A, the manufacturing process of a foldabledisplay apparatus according to the exemplary embodiment is substantiallythe same as that of the exemplary embodiment illustrated in FIGS. 2A and2B until the steps of attaching the protective film 110 on the displaypanel 120 and removing the folding portion A. As illustrated in FIG. 4B,the bumps 111 at both sides of the folding portion A are abraded using aabrader 310. In this state, the bumps 111 at both sides are abraded tohave a height lower than the thickness of the protective film 110. Thatis, the protective film 110 does not have any portion protruding upwardfrom the surface of the protective film 110; rather, the surface of theprotective film 110 is recessed inwardly, forming bumps with an inclinedgroove 112 having a generally concave shape.

Accordingly, since the protective film 110 includes the inclined concavebump 112 and no portion of the protective film 110 is protruding upwardfrom the surface of the protective film 110, no portion of theprotective film 110 prevents or impedes the folding of the foldabledisplay apparatus 100 when the sub-layers 130 are formed as illustratedin FIG. 4C and the foldable display apparatus 100 is folded asillustrated in FIG. 4D.

FIGS. 5A, 5B, 5C, and 5D are cross-sectional views sequentiallyillustrating another exemplary manufacturing process of a foldabledisplay apparatus. According to FIGS. 5A, 5B, 5C, and 5D, bumps 111 atboth sides are abraded to have a matching shape of concavity andconvexity so that the bumps 111 may fit each other when folded.

First, as illustrated in FIG. 5A, the manufacturing process of afoldable display apparatus according to the exemplary embodiment issubstantially the same as that of the exemplary embodiment illustratedin FIGS. 2A and 2B until the steps of attaching the protective film 110on the display panel 120 and removing the folding portion A. Asillustrated in FIG. 5B, the bumps 111 at both sides of the foldingportion A are abraded. In this state, the bumps 111 at both sides areabraded into a convexly shaped bump 113 a at one side and a concavelybump 113 b at the other side, such that bumps 113 a may nest within bump113 b. Then, the sub-layers 130 are stacked as illustrated in FIG. 5C.Accordingly, when the foldable display apparatus 100 is folded asillustrated in FIG. 5D, the convex bump 113 a and the concave bump 113 bat opposing side of the folding area A have corresponding shapes thatmay be nested together. Thus the foldable display apparatus 100 have noobstacles that impede or prevent folding when the top surfaces of theconvex bump 113 a and the concave bump 113 b contact each other. In afolded state, since the convex bump 113 a and the concave bump 113 b arefirmly engaged with each other like a nested, sawtooth, the strength ofthe folding portion A may be further enforced and anti-shock propertiesmay be improved.

Thus, according to the foldable display apparatus and the manufacturingmethod thereof as described above, impedance of folding due to the bumpincidentally formed during removal of the protective film in the foldingportion may be effectively prevented or reduced, and thus the foldabledisplay apparatus may have an improved and/or stabilized foldingoperation.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the inventive concepts are notlimited to such embodiments, but rather to the broader scope of thepresented claims and various obvious modifications and equivalentarrangements.

What is claimed is:
 1. A foldable display apparatus comprising: afoldable display panel having a folding portion about which displaypanel is configured to fold; a lower film on one surface of the displaypanel having two bumps that are spaced apart and disposed adjacent toand at opposite sides of the folding portion; and a sub-layer disposedon the lower film, wherein the folding portion is configured to fold sothat the display panel faces exteriorly of the display panel and thesub-layer faces interiorly of the display panel, and wherein a sum ofheights of the two bumps is approximately less than or equal to a sum ofthicknesses of the two sub-layers at respective sides adjacent to thefolding portion.
 2. The foldable display apparatus of claim 1, whereinthe two bumps have substantially the same height and the height of eachbump is approximately less than or equal to a thickness of thesub-layer.
 3. The foldable display apparatus of claim 1, wherein the twobumps have different heights and the height of at least one of the bumpsis approximately less than a thickness of the sub-layer.
 4. The foldabledisplay apparatus of claim 1, wherein the heights of each of the twobumps are approximately less than or equal to a thickness of the lowerfilm.
 5. The foldable display apparatus of claim 1, wherein the twobumps comprise a concave bump and a convex bump having conforming shapesconfigured to be nested together when the foldable display apparatus isin a folded state.
 6. The foldable display apparatus of claim 5, whereina total height of the concave bump and the convex bump in the nested,folded state is approximately less than or equal to a sum of thicknessesof the two sub-layers at respective sides adjacent to the foldingportion.
 7. The foldable display apparatus of claim 1, wherein an uppersurface of each of the two bumps has a flat shape.